Bit Error Rate (BER), defined as the ratio of the erroneous bits received to the total number of bits transmitted, is a key performance indicator for a communication channel. A good design of a high-speed serial bus needs to meet the BER requirement defined in the specification. Current and future protocols call for BER requirements of 1×10−12-1×10−14, and the BER is expected to be lower in the future.
Factors impacting the BER of a signal link include jitter profiles of transmitter, receiver, and clock distribution, interconnect jitter, coding, and equalization scheme. The random nature of the jitter and bit pattern determines that BER is a statistical indicator, the mean time to error of a channel. A widely used BER representation is the timing/voltage bathtub curve. Determining this curve and its resulting BER at a given eye width margin to achieve BER requirement can be difficult and time consuming.